Centrepoint Marketplace is sort of like the eBay of the Combine. You may do better to buy in bulk from suppliers of whatever you need, but it's worth a look. Be careful of scammers, make sure that what you buy is undocked or easily accessible and not from someone who wants you dead.

Any of the the HC or more experienced players would be happy to check a listing you're considering out for you and make suggestions.

U/U/U (Undocked, Undamaged, Unsheilded) is a good bet as long as the person has a good record of feedback.

If you sell something you want the buyer to send funds before you makeover anything. C/p the coordinates into the listing so they can find the object on the navcomp. You might offer delivery for an extra fee if faction business is such that it looks like you can get away for a week or so.

You might use a community trusted middle for trades over 10m or so. Syn, Dac Kain, Togan Jano and Jude Vatz are all good bets. The buyer and seller agree to the middle and both players send to him, as opposed to each other. He clears everything and sends the respective commodities to the appropriate persons.

Check feedback and check activity of your trading partner for best results. Buying something from someone who's not checking in is no fun.

If you opt for selling via auction, start pretty low with increments of between 100,000 and 500,000.

Other options for trade include NPC Markets which have very basic items, inferior to what Black Bha`lir will provide you with and the Galactic Market which is a Darkness-run auction center. Things purchased there are often docked and otherwise inaccessible. It's recommended that you don't bother with that until you have some ingame experience.

There are also a few IRC channels, such as #swc-traders and #thetraders, which are devoted to trade, but CPM is safer while you figure out who's scamming who.